Why you need to keep the zoom setting constant? Why is zooming to selected items perfectly not good enough?

Zoom level is not constant, it varies. It just must not move from where we manually set it.

Zooming to a 0.5 bar item that contains one note to that one bar fills the screen when you click on a track in the Track List is useless behaviour. Same with 32 bars or whatever. Especially when you then have to noodle your way back to the previous position and zoom level.